Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The use of micro gas turbines (MGTs) for the propulsion of unmanned aerial
vehicles (UAVs) has become an industry standard. MGTs offer better
performance vs. weight than similar sized, internal combustion engines. The front
component of an MGT serves the purpose of compressing air, which is
subsequently mixed with a fuel and ignited to both power the turbine which drives
the compressor, and to produce thrust. Centrifugal compressors are typically used
because of the high pressure ratios they deliver per stage. The purpose of this
project was to design a centrifugal compressor impeller, and to devise a
methodology and the tools with which to perform the aforementioned. A
compressor impeller adhering to specific performance and dimensional
requirements was designed. The new compressor was designed using a mean-line
performance calculation code. The use of the code was vindicated through
comparison with the results from a benchmark study. This comparison included
mean-line, Computational Fluid Dynamic (CFD), and experimental results: the
new design mean-line results were compared to the results of CFD simulations
performed on the same design. The new design was optimised using an Artificial
Neural Network (ANN) and Genetic Algorithm. Prior to and during optimisation,
the ANN was trained using a database of sample CFD calculations. A Finite
Element Analysis (FEA) was done on the optimised impeller geometry to ensure
that failure would not occur during operation. According to CFD results, the final
design delivered good performance at the design speed with regards to pressure
ratio, efficiency, and stall margin. The mechanical stresses experienced during
operation were also within limits. Experimental results showed good agreement
with CFD results of the optimised impeller.
Keywords: micro gas turbine, centrifugal compressor, impeller, CFD,
experimental, optimisation, FEA. / AFRIKAANSE OPSOMMING: Die gebruik van mikrogasturbines vir die aandrywing van onbemande vliegtuie
het ‟n standaard geword in die industrie. Mikrogasturbines bied beter
werkverrigting teen gewig as binnebrandenjins van soortgelyke grote. Hierdie
eienskap verseker dat mikrogasturbines as aandryfmotors vir onbemande vliegtuie
uiters voordelig is. Die voorste komponent van ‟n mikrogasturbine dien om lug
saam te pers, wat dan met brandstof gemeng en daarna aan die brand gesteek word
om krag aan die kompressor en stukrag te voorsien. Sentrifugaalkompressors
word tipies gebruik as gevolg van die hoë drukverhoudings wat hierdie
komponente per stadium kan lewer. Die doel van hierdie projek was om ‟n
sentrifugaalkompressor te ontwerp, en ‟n metode en die hulpmiddels te ontwikkel
om laasgenoemde uit te voer. ‟n Kompressor rotor wat voldoen het aan sekere
werkverrigtings en dimensionele vereistes is ontwerp. Die nuwe kompressor rotor
is met behulp van 1-dimensionele werkverrigting-berekeningskode ontwerp. Die
berekeningsakkuraatheid van die kode en díé van ‟n kommersiële Berekenings
Vloeidinamika pakket is bevestig deur die berekende resultate te vergelyk met die
van eksperimente. Die nuwe rotor is gevolglik deur middel van ‟n Kunsmatige
Neurale Netwerk en Genetiese Algoritme geoptimeer. Die Kunsmatige Neurale
Netwerk is voor en gedurende optimering deur Berekenings Vloeidinamika
simulasies opgelei. Die meganiese sterkte van die geoptimeerde rotor is nagegaan
met behulp van ‟n Eindige Element Analise. Dit is gedoen om te verseker dat die
rotor nie sal faal by die bedryfspunt nie. Berekenings Vloeidinamika resultate het
getoon dat die finale rotor ontwerp ‟n goeie werkverrigting lewer by die
ontwerpspoed, met betrekking tot drukverhouding, bennutingsgraad, en
stakingsmarge. Eksperimentele resultate het goeie ooreenstemming met die
Berekenings Vloeidinamika resultate van die geoptimeerde rotor getoon.
Sleutelwoorde: mikrogasturbine, sentrifigaalkompressor, rotor, Berekenings
Vloeidinamika, eksperimenteel, optimering, Eindige Element Analise.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/71610 |
| Date | 12 1900 |
| Creators | Van der Merwe, Bosman Botha |
| Contributors | Van der Spuy, S. J., Von Backstrom, T. W., Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 123 p. : ill. |
| Rights | Stellenbosch University |
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